The invention relates to an electromagnet system, preferably for a relay, having a bent yoke and having a core which, with one pole end, is opposite an armature and is mounted, by means of one mounting end, with a push fit in a hole in a yoke limb. In addition, the invention relates to a method and to a device for joining the core and yoke together in the case or housing of this electromagnet system.
Electromagnet systems having a winding which is located on a coil former, a core which runs axially through the coil former and a bent yoke which surrounds the coil on two outer sides are generally known and normal. In this case, the core is as a rule pressed with its mounting end in front from the pole side through the coil former into the hole in the yoke limb and, under some circumstances, is fixed by additional measures, such as clipping or welding, to the outside of the yoke. This insertion direction is necessary in the case of most magnet systems since, in order to increase the pole area, the core has an enlarged cross-section at the one pole end, and because of the enlarged cross-section the core would not be possible for it to be pushed in from the yoke side. This conventional type of core mounting is also expedient when the coil former opening is in any case accessible from the pole side or armature side. However, in these cases, the armature cannot be attached until the core has been pushed in, since it is necessary to carry out an adjustment of the pole surface, for example flush with the bearing edge of the yoke, before the insertion of the armature as a rule. Adjustment of the operating air gap, which is desired after installation of the armature, can as a rule be carried out only under more difficult conditions, by displacement of the core.
From U.S. Pat. No. 4,720,909, a method for pressing a core into a yoke hole is already known, and the patent discloses an annular bead which surrounds the hole initially being integrally formed on the yoke limb, so that the mounting path between the yoke limb and the core is extended. The document has also already described the design of the core to be slightly conical towards the mounting end, to be precise in the sense of a cross-section which reduces towards the end, in order to simplify the insertion into the yoke hole. However, in this case as well, the insertion must take place from the pole side, since the core has a pole plate of an enlarged cross-section at the end of the pole side.
However, for various applications it is structurally impossible to insert the core from the armature side or pole side, for example if the armature is, for specific reasons, intended to be installed before the core or if two magnet systems are intended to be mounted on a common base body, aligned with one another, with a short distance between the two cores. For such cases, it is already known from DE-A 3,148,052 for the coil core to be inserted from the yoke limb side and then to be screwed into a specific dimension or position, with the aid of a fine thread. However, the provisions of fine mounting threads between the core and the yoke demands considerable complexity both in the production of the components and in the installation and adjustment.